Transcription

Question 1

What is transcription

Answer 1

The conversion of DNA into RNA using base pairing

Question 2

What is core machinery of transcription

Answer 2

RNA polymerases (depending on RNA type) and proteins that form the initiation complex

Question 3

What are specific factors in transcription

Answer 3

Proteins that induce or repress expression of selective genes (transcription factors)

Question 4

What are the 3 main steps of transcription

Answer 4

Initiation, elongation and termination

Question 5

What is the RNA product complementary and anti parallel to

Answer 5

The template/ non coding strand of DNA

Question 6

What is the RNA product identical to

Answer 6

The non-template/ coding strand of DNA

Question 7

What direction does the coding/ non-template strand run

Answer 7

5’-3’

Question 8

What direction does the RNA product run

Answer 8

5’-3’

Question 9

What direction does the non-coding/template strand run

Answer 9

3’-5’

Question 10

Which RNA polymerase transcribes the gene that encodes most ribosomal RNA (rRNA)

Answer 10

RNA polymerase I

Question 11

Which RNA polymerase transcribes the gene that encodes mRNA

Answer 11

RNA polymerase II

Question 12

Which RNA polymerase transcribes the gene that encodes tRNA and 1 rRNA

Answer 12

RNA polymerase III

Question 13

How many different RNA polymerases are in eukaryotes

Answer 13

3

Question 14

How many different RNA polymerases are in prokaryotes

Answer 14

1

Question 15

What happens during stage 1 of transcription (initiation)

Answer 15

RNA pol binds to the template DNA promoter region and forms the initiation complex

Question 16

What happens during stage 2 of transcription (elongation)

Answer 16

RNA pol synthesises the RNA strand using the template strand pf DNA

Question 17

What happens during stage 3 of transcription (termination)

Answer 17

RNA strand is released at stop signal and the RNA polymerase complex is disassembled

Question 18

What is the TATA box

Answer 18

Promoters on genes transcribed by RNA pol II contain a TATAAA sequence 30bp upstream of +1recognised by the initiation complex and RNA pol II

Question 19

Describe initiation of transcription for a gene transcribed by RNA pol II

Answer 19

1) TAT binding protein (TBP) binds to the TATA box
2) other TFS and RNA pol II are recruited to form the initiation complex
3) RNA polymerase unwinds local regions of DNA so transcription can start at +1 site

Question 20

Describe what happens during elongation of a gene transcribed by RNA pol II

Answer 20

1) RNA pol unwinds the double stranded DNA and moves along the template strand in the 3’-5’ direction
2) RNA nucleotides are added in in the 5’-3’ direction , elongating the RNA strand

Question 21

How does the newly synthesised strand of RNA exit the transcription bubble

Answer 21

Via the exit channel

Question 22

Describe the steps of transcription termination

Answer 22

1) RNA is released and the double helix is rewound
2) RNA pol is released from the template strand and recycled

Question 23

How does transcription termination differ between the 3 RNA pols in eukaryotes

Answer 23

Pol I and III require termination signals but II does not

Question 24

Describe how RNA pol II transcription is terminated

Answer 24

RNA pol II termination does not occur at specific sequences and keeps transcribing beyond the end of a coding sequence, pre mRNA is then processed and cleaved after (AAUAAA) consensus sequence (poly A tail) while transcription is still occurring, cleavage polyadenylation then happens to the pre-mRNA

Question 25

Describe transcription termination with RNA pol I

Answer 25

RNA pol I requires a termination factor to bind to DNA sequence downstream of the terminator sequence

Question 26

Describe transcription termination RNA pol III

Answer 26

Transcription ends after transcribing a termination sequence

Question 27

What is TBF (TATA-binding protein)

Answer 27

A subunit of the transcription Factor II D (TFIID) which binds to the TATA box in the promoter